1. Field of the Invention
The invention relates to aircraft piloting systems and more particularly, in such systems, to a method and a sub-system to check the piloting data presented to the pilot or pilots.
To pilot an aircraft, a pilot needs to have knowledge of a certain number of information elements or data on the status of the aircraft. These data elements come from various pieces of equipment on board and, notably, from a device for the computation of the piloting data. These data are presented by means of standard instruments such as graduated dials, counters, indicators etc., but also, ever increasingly, through images obtained by means of display devices such as cathode-ray tubes, plasma panels, light-emitting diodes, electroluminescent or liquid crystal display panels etc. These image display devices enable the display of several parameters on one and the same surface, either simultaneously or successively, or at the pilot's request. This reduces the number of conventional instruments on the instrument panel.
In certain applications, the data are projected optically before the pilot's eyes, the projection screen being such as to enable the pilot to see the "outside scene" too in his line of sight, whence the term "head-up display" which can be integrated into the pilot's helmet in the case of military aircraft. In this case it is more commonly called a "helmet display".
The transmission lines conveying information between the sensors and the display screens are lengthy and complex, and usually include the above-mentioned devices for the computing of piloting data. As a result, the possibility of erroneous display cannot be ruled out. There is therefore provision for the pilot to make cross-checks between the indications of the display screens and those of the onboard instruments in order to detect inconsistencies. These checks are done in flight at the pilot's discretion. Such checks entail a very major burden of additional work for the pilot.
2. Description of the Prior Art
A known way of detecting an erroneous piece of information without the pilot's intervention lies in setting up a redundancy of the pieces of equipment in the transmission line and in comparing the values given by the redundant pieces of equipment at several points of the line corresponding to different levels of complexity in the preparation of the final information that is displayed. The detection of an inconsistency then prompts at least one alarm which is brought to the knowledge of the pilot.
The redundancy of the equipment leads to an increase in the complexity of the piloting and navigation system as well as the weight of the entire structure. The result thereof is a substantial increase in the cost. Furthermore, it does not enable a comprehensive checking of transmission lines conveying information to the pilot in that it does not allow the information given by non-redundant sensors to be questioned.
Besides, the checks made, both by the pilot and through the redundancy of equipment are "static" inasmuch as they compare two values at a given instant and are not concerned with the changes undergone by the aircraft in the course of time.
An object of the present invention therefore is to set up a system for ensuring the reliability of data used to pilot an aircraft, wherein the checks of consistency between data displayed on the screens and those provided by the sensors and the piloting information computing device are done automatically.
Another object of the present invention is to set up a system for ensuring the reliability of the data used to pilot an aircraft wherein the checks of consistency between the information elements displayed on the screens and those of the onboard instruments are done automatically and continuously, without any active intervention by the pilot.
Another object of the present invention is to set up a system for ensuring the reliability of the data used to pilot an aircraft wherein the changing situation of the aircraft is taken into account.
Yet another object of the present invention is to set up a reliability and safety system such as this without any redundancy of equipment.